Apparatus for the purification of carbon bisulphide



vApr-i114, 1936. A. M. HARKNEss Er AL y 2,037,468

APPARATUS FOR THE PURIFICATION OF CARBON BISULPHIDE Filed Sept.' 16, 1932 ATTORNEY ?atented Apr. 14, 1936 UNITED STATES APPARATUS FOR THE PURIFICATION F ACARBON BISULPHIDE Andrew M. Harkness, Nyack, and om ldaings,

Kew Gardens, N. Y.,

assignors to Generalv Chemical Company, New York, N. Y., a corporation oi New York Application September 16, 1932, Serial No. 633,410 4 claims. (ci. 2oz-154) This invention relates to the purification of crude carbon bisulphide and in particular it relates-to a process and apparatus for the treatment of crude carbon bisulphide vapors or liquids 5 and recovery oi a refined bisulphide product.

Carbon bisulphide may be manufactured by reaction oi heated carbon, in the form oi coke or charcoal `for example, with sulphur vapors passed through the carbon in a retort. The sulphur reacts with the carbon forming carbon bisulphide which, at the temperatures used, is in the form of a gas admixed with vapors oi unreacted sulphur and impurities such as hydrogen sulphide, oxides of carbon, carbonyl sulphide, etc. 'I'hese vapors may be condensed by cooling them to form a` from the retort or from crudecarbon bisulphide liquid obtained from the gas.

It is an object of this invention to provide a process whereby the crude carbon bisulphide may 25 be separatedirom impurities such as the sulphurv which have a boiling point above the boiling point oi carbon bisulphide and also from impurities which, like hydrogen sulphide, have a boiling point lower than the boiling point of carbon bi- 30 sulphide. It is an object oi this invention to provide both a process and an apparatus for carrying out the process, whereby a puriiied carbon bisulphide product may be continuously and economically obtained from a crude bisulphide. It 35 is likewise an object oLthis invention to provide an apparatus suitable for carrying out this distillation and separation of carbon bisulphide from the crude liquid or retort gases. In treating crude liquid carbon bisulphide in ac- 40 cordance with` this invention, the crude liquid is heated to distill of! the carbon bisulphide and impurities having a boiling point lower than carbon bisulphide. Higher, boiling impurities which principally consist oi' sulphur, in part remain be- .45-mndaseresmueintnnmmauonspanam part mingle with the distilled vapors and enter the following stages of treatment of these vapors.

When the gaseous products as they come irom a carbon bisulphide retort are to be treated in ac- 50 cordance with this invention, the gases are cooled to about 135 C., at which temperature high boiling impurities condense out but the carbon bisulphide and low boiling impurities remain in the vapors. f

5 'rne .vapors non the mst distinction or after' the preliminary cooling of the retort gases, are subjected to a rectication treatment which may be carried out in a plurality oi' stages. In a rectication stage, the vapors are introduced into a rectiiying column and are contacted with a reux 5 of condensate from the vapors. The portion ofthe incoming vapors which is not condensed to provide this reux, and which consists principally in impurities having a lower boiling point than carbon bisulphide, are withdrawn and may be 10 treated with Aa solvent for carbon bisulphide to recover carbon bisulphidecarried over with the impurities. 'I'he reuxed condensate is heated in a still to volatilize carbon bisulphide therefrom and a portion of the vapors is passed in con- 15 tact with the refluxed condensate while another portion is withdrawn. 'I'he withdrawn vapors may be condensed as carbon bisulphide product or, without condensation, may be further treated A in additional stages where they are subjected to purification treatments of the same kind as described. above. The reiiuxed carbon bisulphide condensate dissolves the sulphur in the crude vapors.v This sulphur remainsas a liquid residue in the bottom oi the still where the condensate is vaporized and the residue may be returned with the sulphur residue from the preliminary distillation of the crude liquid carbon bisulphide or from the cooling of the retort gases forreaction with carbon to form additional carbon bisulphide. The number of stages of rectication of the vapors employed may be varied according to the degree of purity required in the iinal carbon bisulphide product.

The vapor impurities uncondensed in the above described purification oi carbon bisulphide, which contain the impurities of lower boiling point together with some carbon bisulphide, may be economically treated for the recovery oi their carbon bisulphide content by washing with a solvent 40 such as cool anthracene oil. 'I'he carbon bisulphide may be recovered from solution by heating this oil to vaporize the carbon bisulphide,

'which may be returned for treatment with the vapors distilled from the crude liquid carbon bisulphide. The anthracene oil from which carbon bisulphide has been evolved by heating may be cooled and again used for the absorption of carbon bisulphide from the uncondensed vapors leaving the purication stages.

For a fuller understanding of the nature and objects o! this invention, reference may be had to the following detailed description taken in conl nection with the accompanying drawing which shows a view, partly in cross section, oi an examf ple of the apparatus of this invention suitable for treating a crude liquid carbon bisulphide.

In the drawing, the numeral I indicates a vaporizer vessel provided with a steam jacket 2. The vaporizer is in communication with a pipe of the column where they are met by a descend- A ing current of reiluxed carbon bisulphide from 3 which serves for the introduction of crude liquid carbon bisulphide, a pipe 4 communicating with the bottom of the vaporizer for removal there'- trom of liquid sulphur residue and a pipe 5 leading oi from the top of thevaporizer for conducting away vaporized carbon bisulphide. Pipe 5 communicates with the upper portion of a vertically disposed rectifying column 6. Rectifying column 6 may be provided with bubbling plates, packing, or any other desired means for intimately contacting liquid and gas passed countercurrently in the column. A bottom section oi column 6 is provided with a heater, which in the apparatus shown is a steam jacket.1, and with a draw-off pipe 8. A vapor conduit 9 communicates with the bottom section of column 6 above steam jacket 1. A vapor conduit I and liquid return pipe II communicate between the top of column 6 and the bottom of a cooler I2. Cooler I2 may be, for example, of the shell and tube type with the gases and vapors from column 6 passed inside tubes I3 and a cooling fluid, such as cold water passed around the tubes. A pipe I4 communicates with the top of cooler I2 and serves to conduct gases and vapors from column 6 which are uncondensed in cooler I2 into the bottom of an absorber I5.

A second rectifying column I6 and cooler I1 are provided, like column 6 and cooler I2, with a steam jacket I8 for the bottom of column I6, a draw-oil pipe I9 and a vapor conduit 20 and a liquid return pipe 2I communicating between the column and cooler. 'Ihe top of cooler I1 communicates with a branch 22 of pipe I4. Vapor conduit 9 communicates with an upper section of column I6 thus connecting the pair of columns 6 and I6 in series. A condenser 23 communicates through a vapor pipe 24 with the bottom section of column I6 above jacket I8. A pipe 25 serves for drawing oil? liquid carbon bisulphide product condensed in condenser 23.

Absorber I may consist of a tower containing a packing over which a liquid absorbent for carbon bisulphide introduced into the top of the tower from a pipe 26 and passed downwardly through the tower to outlet pipe 21, is intimately contacted with vapors from pipe I4 entering the bottom oi' thetower and passed upwardly therethrough to gas exit pipe 28. Outlet pipe 21 communicates with a heater' 29 from -which a pipe 30 leads through a pump 3| to a cooled 32 which in turn communicates through pipe 26 with absorption tower I5. A vapor draw-of! pipe 33 leads from heater 29 into a midportion of rectifying column 6. l

In employing the apparatus described above for the purication of crude liquid carbon bisulphide, the crude liquid contaminated with sulphur, hydrogen sulphide, carbon oxysulphide and other impurities is passed 'into vaporizer I wherein the carbon bisulphide 'is vaporized. The vapors and gases comprising a mixture of carbon bisulphide and impurities enter the top portion of the rst rectifying column 6 of the series of two columns. Sulphur contained in the crude liquid carbon bisulphide accumulates in the bottom of the vaporizer and may be periodically withdrawn in a molten condition through pipe 4.

'I'he carbon bisulphide vapors from vaporizer I enter the rst rectifying column near the ton cooler I2 passing yinto the top of the column through liquid return pipe II. 'I'he vapors and gases pass upwardly through the upper portion of column 6 in intimate contact with the carbon bisulphide reflux and enter cooler I2 through Vapor conduit I0 where the carbon bisulphide is condensed and is returned through pipe II into the top of column 6. 'I'he velocities at which the vapors and condensate flow in countercurrent contact with each other in the upper portion of the rectifying column may be materially less than the velocities in the cooler. The uncondensed vapors pass out of cooler I2 through pipe I4 to absorbing tower I5. The condensate ilowing downwardly from the cooler into column 6 carries with it sulphur andother impurities which are in the incoming-vapors from vaporizer I. Low boiling impurities, both entrained and in solution in the condensate, are separated therefrom by the treatment with the incoming vapors, and these vapors in turn are cooled to condense out a portion of the carbon bisulphide in the rectifying column before they pass into the cooler, thus relieving the burden of this portion of the apparatus.

I'he sulphur in solution in the carbon bisulphide is carriedto the bottom of the tower where the carbon bisulphide is vaporized by means of steam introduced into jacket 1. A portion of the vapors thus formed pass upwardly in column 6 in contact with the downwardly ilowing liquid carbon bisulphide and serve to evolve impurities having a lower boiling point than carbon bisulphide from the liquid. These low boiling impurities pass upwardly through the column to be mingled with the incoming crude vapors from pipe4 5. Another portion of the vaporsformed in the bottom of column 6 is withdrawn from the column through vapor conduit 9 and passed into the upper portion of column I6. The concentration of sulphur in the liquid carbon bisulphide in the bottom of column 6 gradually increases, and this solution of sulphur in carbon bisulphide may be periodically Withdrawn through draw-off pipe 8 and either cooled to crystallize out the sulphur and the remaining carbon bisulphide returned to vaporizer I, or the solution without removal of sulphur may be directly returned to vaporizer I.

'I'he carbon bisulphide vapors withdrawn through vapor conduit 9 are of materially greater purity than the vapors entering column 6 from vaporizer I and. if desired, they may be cooled to condense the carbon bisulphide. In the apparatus shown in the drawing, however, they are subjected in column I6 and cooler I1 to a treatment like that of the vapors from vaporizer I in column 6 and cooler I2. Thus, in

column I6, the incoming vapors from conduit 94 pass upwardly through the upper portion of the column in contact with downwardly flowing carbon bisulphide from cooler I1 and thence to cooler I1 where carbon bisulphide is condensed from the vapors and the condensate returned through liquid return pipe 2I to the'top of column I6. The uncondensed vapors or gases pass out oi the cooler through branch 22 to pipe I4 and thence to absorbing tower I5. The condensed liquid carbon bisulphide flows downwardly through column I6 and in the bottom of the column'is heated to vaporize carbon bisulphide. A portion of the vapors formed in the bottom oi' column I6 rises in the column in countercurrent to the descending liquid to evolve therefrom lower boiling impurities and another portion of the vapors is drawn oi from the bottom section of column I6 through pipe 24 to condenser 23. As sulphur accumulates in the liquid in the bottom of column I6, the solution is withdrawn from the column and treated as described above for the solution withdrawn from column 6. In condenser 23, the purified vaporous carbon bisulphide is condensed to a liquid which is withdrawn from the cooler through pipe 25 as puriiied carbon bisulphide product.

The gaseous and vaporous impurities passing out ofthe tops of coolers I2 and II principally consist of compoundsof a lower boiling point than carbon bisulphide but also contain carbon bisulphid'e vapors. In absorption tower I5, these gases and `vapors are contacted with a liquid absorbent for carbon bisulphide such as, for example, anthracene oil which absorbs the carbon bisulphide. gases and vapors pass out of absorption tower I5 through pipe 28 and may be treated in any desired manner. The solution of carbon bisulphidev in anthracene oil is passed to heater 29, whereby raising the temperature of the solution carbon bisulphide is vaporized 1 therefrom. The heated oil from heater 29 is recirculated by means of pump 3| through a cooler 32, where the oil is cooled to a temperature suitable for again returning it to absorption tower I5 for treatment of additional quantities of gases and vapors entering from pipe I4. The vapors evolved from the oil in the heater are returned through draw-off pipe `."13 and introduced into the mid-portion of rectifying column 6 where they pass upwardly in contact with the descending ow of liquid carbon' bisulphide and are treated in the column and cooler I2 with the crude carbon bisulphide vapors from'vaporizer I. The low boiling vapors are thus.,separated from the carbon bisulphide and any oil which may be carried with the vapors and pass out of column 6 and cooler I2, while the oil and carbon bisulphide are carrieddown into the bottom of the column. The carbon bisulphide is vaporized and recovered as pure product, while the oil remains in the sulphur-carbon-bisulphide solution withdrawn from the column through pipe 8.

When the impure gases from a carbon bisulphide retort are to be treated without -iirst condensing crude liquid, the apparatus shown in the Idrawing may be modiiied to substitute a cooler for the vaporizer. 'I'he retort gases are then passed through the cooler where their temperature is lowered suicient to condense out high boiling impurities but not enough to condense the carbon bisulphide. The cooled vapors are then passed through pipe 5 of the apparatus,-

y is not limited to the speciiic features of the example. Thus, while we have described an apparatus employing a series of two rectlfyingv columns and associated coolers, a greater or lesser number may be employed depending upon the degree of purity required in the nal product.

The remaining unabsorbed- Y heater. v

2.'In combination in an apparatus for the purification of crude liquid carbon bisulphide,

a vaporizer, a rectifying column, a vapor con-l duit communicating between said vaporizer at a' point above the normal liquid level in said vaporizer and the upper portion of said column, a cooler, a vapor conduit and a liquid'return conduit communicating between the top of said column and said cooler, a heater for the bottomI portion of the column and a vapor conduit communicating with the bottom portion of the columnabove said heater, an absorbing tower, and a gas conduit communicating between the absorbing tower and the aforesaid cooler.

3. In combination in an apparatus for the purification of crude liquid carbon bisulphide, a

vaporizer, a plurality of vertically arranged rectifying columns and coolers, means connecting the top of each of said columns with a cooler arranged'for flow of vapor to the cooler and re'- turn of liquid. to the column, heaters for the bottom portions of said columns, a vapor conduit connecting a bottom section of one of a pair of said columns with an upper section of the other column of the pair, said columns being thus' connected in series, a vapor conduit connecting said vaporizer at a point above the normal liquid level in said vaporizer with an upper section of the rst of the-,columns in the series,

and a condenser in communication with the bottom section of the last ofsaid columns in the series.

4. In combination in an apparatus for the purication of crude liquid carbon bisulphide, av

vaporizer, a plurality of vertically arranged rectifying columns and coolers, means connecting the top of each of said columns with a cooler arranged for ow of vapor to the cooler and return of liquid to the column, heaters for the bottom portions of said columns, a vapor conduit connecting a bottom section of one of a. pair of said columns with an upper section of the other column of the pair,` said columns being thus connected in series, a vapor conduit connecting said vaporizer at a point above the normal liquid level in said vaporizer with an upper section of the rst of the columns in the series, a condenser in communication with the bottom section of the last of said columns in the series, an absorption tower, a heater and a cooler, and means for recirculating a fluid therethrough, and a vapor conduit connecting said heater and a mid.- portion-of the rst rectifying column of the aforesaid series of columns.

ANDREW- M. HARKNESS. CARL IDDINGS. 

